This invention relates in general to waste disposal and in particular to a new and useful plant arrangement for a low temperature carbonization of waste materials.
Waste materials according to the invention include household waste and industrial waste as well as chemical residues developing noxious matter or hazardous substances such as various dioxines, furanes, CO etc.
Plants and arrangements for the incineration of harmful waste are in use by the present invention as a signal, wherein a revolving tubular furnace is followed by a secondary incineration chamber. This incineration chamber has a temperature between 1200.degree. and 1400.degree. and a gas velocity of 2-4 m/sec.
A secondary incineration chamber downstream of the incineration furnace for chemical waste is known from German DE-Patent Application No. 36 25 397, which has not been pre-published. Herein the burners in the secondary incineration chamber are concentrated in a certain area of the chamber.
The German Patent Application No. P 37 30 339, which is also older and gas not pre-published either, suggests a plant arrangement for the low-temperature carbonization of waste materials and contaminated matter, wherein an extractor for residues from a low-temperature carbonization drum is followed by a step grate equipped with an incineration means which in turn is followed by a secondary incineration chamber and a heat-recuperation device, preferably a waste heat boiler with a steam collecting drum. In these systems and devices the incineration or carbonization gases enter the secondary incineration chamber as a heat dissipating medium This is also possible in the plant or arrangement according to the invention. However, the incineration gases may also be from a different source.
The invention provides a heating system for a low-temperature carbonization plant which is substantially free from corrosion and furthermore permits the transformation of gases hazardous to the environment into those with a reduced content of hazardous matter and to achieve this by means which are simple in design.
The arrangement according to the invention guarantees that the gases charged with hazardous matter entering the secondary incineration chamber at a temperature of ca. 1400.degree. are kept at a temperature of 1200.degree. or above during their period of dwell of 1.0 to 5.0 sec., preferably 2 sec., so that during this time a transformation into a gas with a reduced amount of hazardous matter may take place. Also, the heat withdrawn from the gas in the secondary incineration chamber is of advantage to the low-temperature carbonization process because the heating gas of the low-temperature carbonization device is heated up in the secondary incineration chamber, the heating-up taking place in a closed-loop cycle between the low-temperature carbonization device and the heat exchanger of the secondary incineration chamber, thus avoiding corrosion of the parts.
German Patent DE-OS No. 35 04 810 discloses a process for the thermal transformation of dioxin. In this patent it is described in respect to a coke battery which is arranged parallel to a pyrolysis plant and the battery in the plant exchanges gas into a secondary incineration chamber which is apparently provided for the burning of a dioxin beyond a temperature of 1200.degree. C. Such an arrangement is distinct from the present arrangement wherein the heating gas of a low temperature carbonization plant is led through a closed loop cycle to the low temperature carbonization device and the heat exchanger of the secondary incineration chamber. With applicant's invention which relates primarily to waste treatment the heating device for the low carbonization of the waste material is kept substantially corrosion free. This is achieved because the heating gases are circulated back to a separate heat exchanger. Thus, it is apparent that the present invention is basically dissimilar from a pyrolysis plant in which a gas converter of a coke bed is used to feed the burner of a heating gas generator after a gas purification.
Accordingly it is an object of the invention to provide an improved method of treating waste material which comprises subjecting the waste material to a heating in a closed container used in a heating gas which is circulated in heat exchange relationship with the chamber and effects a low temperature carbonization of the waste material and thereafter circulating the heating gas to a separate heat exchanger to maintain the heating gas at a temperature of over 1200.degree. C. for from 1 to 5 sec. and then circulating it back to the closed container.
A further object of the invention is to provide a device for effecting waste treatment which includes a low temperature vessel having a waste treatment chamber through which waste material is passed in order to be carbonized and which includes a container around the chamber for the passage of a heating gas for heating the waste material in the container treatment chamber and which also includes a secondary treatment chamber which includes a heat exchanger having a heat exchange passage connected to the container and providing a close circulation of the heating gas from the container to the secondary treatment chamber and back again in a closed loop cycle.
A further object of the invention is to provide a waste treatment system which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding if the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.